CastleMountain castle (yamajiro)Next 100 Fine Castles No. 190
What makes this castle distinctive
A mountain with cliffs on three sides, walled with stone only where the cliffs break off, so that the whole peak works as a stone castle.
Why?
Mount Tsunomure is a butte, a hill left standing after the land around it eroded away, with sheer cliffs on every side except the south. Mori Takamasa, who remodeled the castle in the late 16th century, built stone walls only where the cliffs had gaps. Kusu Town explains that if you count the cliffs as natural walls, the idea was to enclose the whole castle in stone.[1]
The great stone wall of the second enclosure's south gate
Where
The south side of the second enclosure, at the main gate site on the way up from the third-enclosure parking area to the summit.
What to look at
The stone wall, up to about 7 m high and some 100 m long, and the square gateway projecting outward (sotomasugata koguchi).
Why it's interesting
This is the largest stone wall in the castle and is thought to have been its front (ote). The town explains that it was meant not only for defense but also to impress people looking up from the castle town at the southern foot of the mountain. Excavations found the sites of turret gates of the same size at both the south and west gateways of the second enclosure.[1][4]
Can you see it?
Visible from outsideFree to visit; stone-wall repair work may be in progress.
The north side of the main enclosure, the second enclosure and the third enclosure.
What to look at
The places where cliff and wall meet, and the walls around the third enclosure.
Why it's interesting
All the stone walls Mori Takamasa built sit in gaps in Mount Tsunomure's cliffs. Instead of walling everything, the builders made use of the natural cliffs, which is what makes this mountain castle distinctive. The third enclosure was walled all around, and a climbing wall once ran up the slope toward the second enclosure.[1]
Can you see it?
Visible from outsideFree to visit; some paths are slippery.
03
Traces of the medieval earthen fort
Where
Around the summit enclosure and on the southern slopes.
What to look at
Artificially steepened slopes (kirigishi), narrow terraces (obi-kuruwa), and rows of vertical trenches cut down the slope.
Why it's interesting
Tsunomure shows both the earthwork castle of the Warring States period and the stone-walled castle that followed. That is why it was made a National Historic Site in 2005, as important for understanding the shift from earthen castles to stone-walled ones.[1][5]
Can you see it?
Visible from outsideFree to visit. The Bungo Mori Domain Museum at the foot of the mountain shows maps and video from a 3D laser survey of the site, useful before you climb.
At a glance for visitors
Nearest station
90 min walk from JR Bungo-Mori Station
Climb
Steep climb
Time neededEditors' estimate
About 30 minutes round trip from the third-enclosure parking to the summit; allow half a day if you hike from the foot.
Admission
100 yen for visitors from outside the town (free for high school students and under-18s, and for visitors to the Kurushima Takehiko Memorial Museum); free for residents
Hours
9:00–16:30
Access
Open to visitors
The site is open to visit freely. The temporary construction road is closed to non-construction vehicles, but part of it doubles as a (slippery) footpath. Do not litter or light fires. The Continued Top 100 Castles stamp is kept at two places, the Bungo Mori Domain Museum (inside Warabe-no-Yakata) and Kusumachi Mersan Hall, and is unavailable outside their opening hours.
Kusu sits in a basin about 330 m above sea level, ringed by flat-topped mesas. Mount Tsunomure, at the basin's northern edge, rises some 230 m above it and is surrounded by cliffs on all sides but the south. It guarded the route between Kusu and Buzen (today's northern Oita), and in the Warring States period the Otomo lords of Bungo valued it as a border castle.[1][4]
02
Historical record
From the Mori clan's fort to Mori Takamasa's stone castle
Tsunomure is said to have been the castle of the Mori, one of the local lords known as the Kusu district warriors. It was strengthened under Otomo direction in the Warring States period and, according to tradition, never fell, even to the Shimazu invasion of 1586–87. After the Otomo lost their domain, Mori Takamasa arrived in 1594 and began turning it into an early-modern stone-walled castle, though the remodeling was only partial.[1][4]
03
Tradition
A domain that left its castle unused
In 1601 the Kurushima family, the only one of the three Murakami pirate houses of Iyo to become daimyo, arrived and built their administrative residence (jinya) at the southern foot of the mountain. The Kurushima kept the mountain as a protected domain forest and did not use it as a castle. Tradition says the eighth lord, Kurushima Michihiro, had castle-like tiers of stone walls built around a shrine on a hill west of the jinya, to fulfill his dream of owning a castle.[1]
04
Historical record
National designation and wall repairs
The castle ruins were designated a National Historic Site in 2005 and chosen as one of the Continued Top 100 Japanese Castles in 2017. Stone-wall repairs are ongoing, and part of the temporary construction road doubles as a walking path. The mountain also lies within Yaba-Hita-Hikosan Quasi-National Park and a wildlife protection area.[1][2][6]
Chosen as one of the Continued Top 100 Japanese Castles[7][6]
Buildings and remains
The keep today
No keep was built
No record of a keep has been found; the Japan Castle Foundation lists none.
The site today
The summit of Mount Tsunomure (577 m) preserves medieval scarps, terraces and trenches alongside early-modern stone walls, gateways and turret-gate sites. No buildings remain. A road leads up to the third enclosure, and the Bungo Mori Domain Museum stands at the foot. Stone-wall repairs are under way.
Main buildings
Original
Second enclosure south gateway walls
Up to about 7 m high and 100 m long, the largest in the castle; thought to be the main approach.[1]
Site only
South and west turret gates of the second enclosure
Sites of turret gates of the same size have been found; foundation stones remain at the west gate site.[1]
Original
Third enclosure walls
Walled all around; a climbing wall once ran up toward the second enclosure.[1]
Key facts
Type
Castle
Setting
Mountain castle (yamajiro)built on a mountain; expect a climbEditorial article
Period
Medieval (c.1185–1570s), Early modern (1570s–1871)Editorial article
Keep (tenshu)
No keep was builtthe castle never had a keepEditorial article
National Historic Site (Tsunomure Castle ruins) (2005)Editorial article
Selection
Next 100 Fine Castles No. 190Japan Castle Foundation
Visiting
Access
Open to visitors
The site is open to visit freely. The temporary construction road is closed to non-construction vehicles, but part of it doubles as a (slippery) footpath. Do not litter or light fires. The Continued Top 100 Castles stamp is kept at two places, the Bungo Mori Domain Museum (inside Warabe-no-Yakata) and Kusumachi Mersan Hall, and is unavailable outside their opening hours.
About 1 hour 30 minutes on foot from the station to the third enclosure, per the Kusu tourism association. The Bungo Mori Domain Museum at the foot is about 30 minutes' walk from the station, or 3 minutes from the Morimachi bus stop.[5][4]
Checked: 2026-10-04
Hours and admission
Bungo Mori Domain Museum (inside Warabe-no-Yakata)
Hours
9:00–16:30
Closed
Mondays (or the first non-holiday after a Monday holiday), December 28 – January 4
Admission
100 yen for visitors from outside the town (free for high school students and under-18s, and for visitors to the Kurushima Takehiko Memorial Museum); free for residents[3][4]
Checked: 2026-10-04
By car / parking
About 15 minutes by car from Kusu IC on the Oita Expressway to the third enclosure, where there is parking for a few cars at the site entrance.[4][5]
Checked: 2026-10-04
Grounds opening hours
The site is open mountain land; no set hours were found.Checked: 2026-10-04
Time neededEditors' estimate
About 30 minutes round trip from the third-enclosure parking to the summit; allow half a day if you hike from the foot.
Steps, slopes and footing
A mountain castle: from the third enclosure a trail climbs to the summit. The hiking course from Mishima Park at the foot takes about an hour, per the tourism association. The temporary construction road can be slippery.[5][1]
Wheelchairs and strollers
Mountain paths make the site unsuitable for wheelchairs.[5]Checked: 2026-10-04
Toilets and rest
Mishima Park at the foot has toilets (tourism association pamphlet); toilets at the ruins are not confirmed.[5]
English signs / audio guide
Not confirmed
Seasons
No official seasonal information was found.
Photography
Not confirmed
Works, closures and restrictions
A temporary road for stone-wall repair vehicles is in place and other vehicles may not use it (town notice, May 2023).[1]Checked: 2026-10-04
Suggested routes
30 minutes round trip: third enclosure to the summit 30 min
Start from the parking area in the third enclosure
See the great stone wall of the second enclosure's south gateway at the main gate site
Pass the Oike-no-dan terrace and the lookout
Continue past the west gate site (second enclosure) to the summit enclosure
Return the same way to the third enclosure
Time follows the Kusu tourism association pamphlet ("an easy 30 minutes round trip"). The hiking course up from Mishima Park takes about an hour.
Museum at the foot of the castle mountain, showing maps and video from a 3D laser survey of the ruins and surrounding terrain. The Continued Top 100 Castles stamp is kept here.[1][3]
Checked: 2026-10-04
Editors' guide
An editorial guide based on sources and confirmed information — not a first-hand visit report.
Who will enjoy it
Good for mountain-castle hikers and anyone interested in how earthen forts gave way to stone-walled castles. By car you can drive up to the third enclosure and see the walls without a full climb.
What makes it interesting
Start with the great wall at the second enclosure's south gateway and notice how the cliffs and stone walls connect. At the summit, look for medieval earthworks such as scarps and terraces to see how two eras of castle-building overlap.
Before you go
Stone-wall repairs are under way and the temporary road is slippery. The third-enclosure parking holds only a few cars. The stamp is not at the ruins but at the Bungo Mori Domain Museum and Kusumachi Mersan Hall, and the museum is closed on Mondays.
Ways to enjoy it
Before climbing, study the 3D terrain map and video at the Bungo Mori Domain Museum so you know the layout of the enclosures. Combine the visit with the former Kurushima garden at the foot and the shrine the castle-less Mori lords walled like a fortress, and you will see how the mountaintop castle and the jinya below relate.
Photos
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Open questions
One tradition says the Mori built the castle in the Koan era (1278–88), but it is first confirmed in records in 1475.
The town dates the high walls to Mori Takamasa (1594–1600), but some researchers argue they were built after the Kurushima arrived.
Most sources give the mountain's height as 577 m. Sources differ on whether the Shimazu attack came in 1586 or 1587.
The photos date from 2009 and may not reflect later wall repairs. English signage, photo rules and toilets at the ruins could not be confirmed.
MukaiCC BY-SA 3.0Wikimedia Commons
